The dehydration of lactic acid to produce acrylic acid is a renewable alternative to the mostly used production of acrylic acid from propene. In this review, the recent developments and state of the art for the dehydration of lactic acid to acrylic acid are presented and critically commented. The most recent publications on the topic are discussed inetail with respect to the observed catalysts and process performance data. Among the different catalysts developed, three main groups can be distinguished: zeolites, sulphates, and phosphates. The latter, especially hydroxyapatites, have recently attracted the attention of academics in particular. The three families of catalysts are discussed and the recent developments and technical drawbacks in the gas phase dehydration are reported.
Biomass valorization is a booming field. Especially, the valorization of platform molecules by catalytic processes has driven a large interest in the recent years, and many groups are actively working on the transformation of biosourced substrates to a variety of upgraded chemicals. In this context, in the present paper we put in perspectives the scientific works of our research team. We first classified catalytic transformations of industrial interest according to the number of carbons of the starting material, from C1 to C6. They involve, among others, acid catalysts (e.g., for glycerol dehydration), redox catalysts (e.g., for 5-HMF conversion to diformylfuran), acid and redox catalysts (e.g., for direct acetalization of alcohols), or complex multifunctional catalysts, especially for the Guerbet reaction. Further, we also developed what we called 'toolboxes,' which are general concepts or technologies with a broader field of applications. For example, we adapted the two zones fluidized bed reactor (TZFBR) concept to the single reactor continuous regeneration of coking catalysts. Further, we designed a completely new high throughput platform enabling synthetizing, characterizing and testing the performances of many catalysts for considerably accelerating the catalysts discovery/optimization loop.
The deoxydehydration (DODH) of glycerol was studied using several Re‐based catalysts in the liquid phase under atmospheric pressure conditions. The best performance was observed over 10 wt.% ReOx/Al2O3 with 2‐hexanol as a reductive agent giving allyl alcohol with an exceptional yield of 91%. The reaction was confirmed to be catalysed heterogeneously, since the reaction stopped upon removal of the catalyst by hot filtration. The corresponding catalyst was further successfully reused three times without any leaching of rhenium species, as shown by elemental analysis. Based on the characterisation of the fresh and the spent catalyst by XPS and Raman spectroscopy, a reaction mechanism is proposed, which involves the redox‐couple Re(V) / Re(VII).
High-throughput (HT) methodology was applied for the synthesis, characterization and catalytic testing of Cu-and Ni-based catalysts for glucose hydrogenation. Design of Experiment (DoE) was used in all steps. The deposition and reduction of both metals was performed using chemical reduction with hydrazine method. In total 36 catalysts were synthetized, characterized and tested in 5 days. The amount of metal deposited on the support was chosen as the discriminative and determining parameter. The catalysts were tested at low temperature in the hydrogenation of glucose to sorbitol. The results showed that chemical reduction-precipitation method could be performed using fully automatized robots. The deposition of the metals strongly depended on the nature of the support, the temperature of the reduction and hydrazine/H2O ratio. The maximum metal precipitation occurred at higher temperature (70°C) and lower N2H4/H2O ratio (0.04 mol/mol) in both cases. The results clearly showed that glucose conversion is higher for the catalysts synthesized at 70°C compared to the catalysts synthesized at 50°C, irrespective of the metal precursors, supports and hydrazine/water ratios employed during catalysts syntheses. With a total timespan of around 5 days we showed that HT methods applied to all the steps (synthesis, characterization and testing) can significantly reduce the time needed to develop a new catalytic process.
The catalytic dehydration of 1,3-butanediol into butadiene was investigated over various aluminosilicates with different SiO2/Al2O3 ratios and pore architectures.
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